It is a common practice to provide illumination for portions of control panels for radios and other audio devices to facilitate their use at night or during other conditions in which the ambient lighting is low. For example, it is a common practice to illuminate the tuning dial of a radio. Typically, the frequencies in the AM and/or FM bands are marked on opposed parallel scales extending longitudinally on a rectangular, transparent tuning plate. A tuning indicator is moved back and forth behind the tuning plate to the appropriate frequency, and light bulbs or other illuminating devices are used to backlight the tuning plate so that the frequency designations may be viewed at night, or under other poor lighting conditions. The tuning plate is mounted in an opaque frame in which push buttons, knobs, and other switches are mounted.
More recently, with the advent of digital technology, the control panel of an audio device has changed significantly. For example, the backlit tuning plate is replaced by a light emitting diode (LED) or liquid crystal display (LCD) panel or screen which displays the characters and other indicia corresponding to the station currently being received by the radio and other operating information. Typically, those displays are illuminated by light bulbs or other light sources located at the edges of the screen. Further, the front portion of the control panel in which push buttons, switches and the character display are mounted is made from an opaque plastic or metal material; and often, the control panel is black in color. The push buttons and switches mounted in the control panel are operatively connected to electronic devices within or behind the control panel. In order to facilitate their use at night, the push buttons are typically made of transparent "LEXAN" polycarbonate material, acrylic, or plexiglass. A label or other indicia is silk screened in wax on the front surface of the push button. The visible surfaces of the push button are then painted black or another opaque color; and thereafter, the wax is removed which leaves the shape of the label or indicia extending through the paint and onto the clear plastic front surface. Light bulbs are mounted behind the control panel and their light passes through the clear plastic push button to illuminate the labels or indicia on the front surface of the interior of the push buttons.
In use, the only light provided by the control panel is the light from the LCD character display and the light from the indicia on the push buttons. Such light is minimal; and given the number of push buttons and switches on contemporary control panels, the use of such a control panel at night, or in poor lighting conditions, has the disadvantage of being somewhat difficult to use. Further, as will be appreciated, the manufacture of an illuminated push button is time consuming, requires several manufacturing process steps, and therefore has the disadvantage of being relatively expensive.
As an alternative to illuminating indicia on the front of the push buttons, another control panel construction provides a number of cutouts immediately above or otherwise adjacent to the push buttons. Behind the opaque control panel is a plastic diffuser which is molded to have projections mating with the cutouts in the panel. Those mating projections extend through the cutouts to the front surface of the panel and are finished with the front panel surface to appear as a silver finish during the daylight. Typically, LED's are used with the diffuser to illuminate the projections with color as desired at night. Once again, those projections provide minimal illumination and have the disadvantage of being confusing and difficult to use. In addition, the manufacturing process of providing precisely mating molded pieces, as well as finishing those pieces, requires additional manufacturing steps which add cost to the manufacturing process.